The Casio fx-991 CW is the new upgraded version of the Casio fx-991 EX (Casio’s most advanced scientific calculator), containing additional features, to include a high definition display and improved menu navigation. Approved for Key stages 3, 4 and 5, recommended for Advanced GCSE, A/AS level and Highers. Allowed in every UK exam where a calculator can be used. The Casio fx-991 CW is Casio’s most advanced scientific calculator with 540 + mathematical functions. The large Natural Textbook Display shows mathematical expressions like roots and fractions as they appear in your textbooks which increases comprehension because results are easier to understand.